Merged context creation BacMatch workaround from 2.7.1.

readme.html

@@ -292,6 +292,7 @@ version of GLFW.</p>
   <li>Removed <code>GLFWCALL</code> and <code>GLFWAPIENTRY</code> macros for stdcall calling convention</li>
   <li>Bugfix: The default OpenGL version in the <code>version</code> test was set to 1.1</li>
   <li>Bugfix: The OpenGL profile and forward-compatibility window parameters were not saved after context creation</li>
+  <li>[X11] Bugfix: Calling <code>glXCreateContextAttribsARB</code> with an unavailable OpenGL version caused the application to terminate with a <code>BadMatch</code> Xlib error</li>
   <li>[Win32] Removed explicit support for versions of Windows older than Windows XP</li>
 </ul>
 

src/x11/x11_window.c

@@ -45,6 +45,17 @@
 #define Button6			6
 #define Button7			7
 
+//========================================================================
+// Error handler for BadMatch errors when requesting context with
+// unavailable OpenGL versions using the GLX_ARB_create_context extension
+//========================================================================
+
+static int errorHandler(Display *display, XErrorEvent* event)
+{
+    return 0;
+}
+
+
 //========================================================================
 // Checks whether the event is a MapNotify for the specified window
 //========================================================================
@@ -580,12 +591,21 @@ static int createContext(_GLFWwindow* window, const _GLFWwndconfig* wndconfig, G
 
         setGLXattrib(attribs, index, None, None);
 
+        // This is the only place we set an Xlib error handler, and we only do
+        // it because glXCreateContextAttribsARB generates a BadMatch error if
+        // the requested OpenGL version is unavailable (instead of a civilized
+        // response like returning NULL)
+        XSetErrorHandler(errorHandler);
+
         window->GLX.context =
             window->GLX.CreateContextAttribsARB(_glfwLibrary.X11.display,
                                                 *fbconfig,
                                                 share,
                                                 True,
                                                 attribs);
+
+        // We are done, so unset the error handler again (see above)
+        XSetErrorHandler(NULL);
     }
     else
     {